Electric fuse



July 2, 1940. J, T, VATAVA 2,206,794

ELECTRIC FUSE Filed Feb. 16, 1959 nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn nPatented July 2, 1940 UNITED STATES PATENT OFFICE 8 Claims.

This invention relates to an electric fuse for an overload circuitbreaker and it aims to provide a novel construction which is adjustablefor immediate vreuse after blowing or interruption of an electriccircuit wherein it is used.

Another object is to provide such a fuse structure having a fuse memberadapted to contact with an electrode, which contact is destroyed by aslight melting or evaporation of the fuse at the zone of contact whenthe short circuit occurs, and which fuse is screw threaded or otherwiseadjustable so that it may be thereafter immediately adjusted to againestablish the contact and accordingly the electric circuit.

A further object' is to provide such a construction wherein the fuseelement of metal, preferably the `soft metals such as lead, aluminum,Woods metal because of their lower melting points, will establish theaforesaid contact with a carbon element or equivalent.

The more specific objects and advantages will vbecome apparent from aconsideration of the description following taken in connection withaccompanying drawing illustrating a number of operative embodiments ofthe invention.

In said drawing:

Figure l is a view partly in elevation and partly in section through oneform of the fuse;

Figure 2 is a view partly in elevation and partly in section through amodified form of fuse;

Figure 3 is a vertical sectional view taken substantially centrallythrough another modified form of the invention;

Figure 4 is across sectional view taken on th line 4-4 of Figure 3;

Figure 5 is a cross sectional view taken on the line 5-5 of Figure 3;

Figure 6 is a central vertical sectional view through a further modifiedform of the invention;

Figure '7 is a front elevation of a nal form of the invention, and

Figure 8 is a longitudinal sectional view taken on the line 8-8 ofFigure '7.

Referring more specifically to the drawing, One form of the invention isshown in Figure 1, being an L-type of fuse plug. In this form, a fusestrip or element is designated 26 and is in the form of an externallyscrewV threaded rod, being of any suitable metal, but preferably. a softmetal such as lead, aluminum, Woods metal or the like, because of theirlow melting points. The body in this form is designated lll', having ascrew threaded conductor shell Il thereon and a cap I3 thereon, theshell Il' and cap I3 being conductors, with the shell ll threaded todetachably (Cl. 20G-125) connect with a conventional socket. A nut 2l isstationarily secured within the body Ill', being of conducting metal andhaving a conductor 28 connecting it to the shell Il'. An electrode orcontact block 29 is rigid in the base of body I0 and a conductor 30connects the same to the cap I3. Body 29 may be of any suitable materialand for instance is preferably of carbon and when the circuit is closed,the fuse member 26 contacts at its lower end with such block 29. 'I'hethreads of the screw member 26 engage those in the bore 3| of fixed nut21 and the screw fuse 26 is operable through the turning of a knob 32thereon, located exteriorly thereof. Fuse strip 26, exteriorly of thebody I0', may be surrounded by a tube 33 of suitable insulation, such asa flexible rubber tube, which will collapse or yield to permit inwardadjustment of the screw 26.

In the operation of this form of Figure 1, a short circuit will burnaway that portion of the 20 lower end of fuse strip 26 contacting thecarbon block 29, thereby opening the circuit. Such circuit may beinstantly. closed through the adjustment of the knob 22 which screws thefuse member 26 again into contact with the block 29.

The form of Figure 2 is substantially like that of Figure 1. It differstherefrom with respect to prong contacts 34 and 35, adapted to engage ina wall receptacle or otherwise, instead of having screw connection withthe receptacle or socket and such prongs correspond in the circuit tothe shell Il' and cap I3', respectively. The insulating body, here shownat Illa is advantageously shaped differently from that at I0. Prong 34has a conductor 36 leading therefrom to a nut 21' corresponding to thatat 2l and the prong 35 has a conductor 31 leading therefrom to the block29' corresponding to that at 29.

In Figures 3 to 5, a screw rod or strip form of fuse is employed at 26aof the same material as that at l1 and 26, which co-acts with a block orcontact 29a, preferably of carbon, in the same manner that the fusemember 26 co-acts with the block 29 in the form of Figures l and 2. Thisform has a body Illa of insulation adapted to be screwed into a socketof a conductor band or shell Ha, disposed in conducting relation with anL-shaped conductor bracket 38 which has a screw threaded opening 39 inwhich the fuse rod 26a is adjustably threaded. A cap 13a correspondingto that at I3', is of conducting material and in conducting relationwith the carbon block 29a. A closure 40 may be provided over the upperend of body Illa and a collapsible insulating tube 33a, like that at 33,may surround the fuse rod 26a exteriorly of body I 0a.

In Figure 6, I have shown an example of the practice of the inventionwith an electrode of mercury or quicksilver, the latter being shown at4I and suitably retained in a Well 42 within a body of insulation 43.Such body 43 has a conductor shell IIb of'screw form for engagementwith-a socket which is in conducting relation with a bar conductor 44embedded in the body 43 and having a screw threadedY opening at 45operatively engaged by the screw threads of a fuse rod 46 similar tothose employed at 26 and 26a and of the same material as such fuse rods.Fuse rod 46 by means of a knob 41 is adjustable and its inner endco-acts with the .mercury electrode 4I in the same manner as the rods 26and 26a co-act with their carbon contacts 29 and 29a, respectively, morespeciiically, the adjacent end of the fod 46 burning away upon shortcircuit, at the zone of engagement of contact with the mercury 4|, andlater the rod being screwed to again contact the mercury and establishthe circuit, through operation of knob 41. The mercury may be suppliedto the well 42 through alined passages 41' and 48 in the body 43'and bar44 and such passage is normally closed by a screw plug' or anyequivalent at 49.

Since this form of the invention is also of the screw type, it has acentral contact 50 and a conductor 5I leads therefrom to a conductor 52,exposed in the mercury 4I and -having its upper surface protected bysuitable insulating material 53 extending inwardly from the wall of thewell 42, and preventing direct contact of the fuse rod with the contactor block 52.

In Figures 7 and 8, a form of the invention is shown for a box more likethe old type of fuse outlet boxes. This box has an attaching plate at 54adapted to be fastened vto a Wall or support as by means of screws orfastenings passed through lugs 55 at the corners thereof. A box sectionis built from plate 54 by providing a surrounding wall 56 and a rigidlymounted but detachable cover 51. A bracket of insulation 58 carried bythe plate 54 mounts a contact block 59 of suitable conducting materialand for instance carbon, a wire from one side of the circuit as at 60being connected to the bracket 58. Block 59 is engaged by a fuse rod 6|of the same material as the strips or rods I1, 26, 26a and 46 andadapted to function in a similar manner with respect to the block 59.Rod 6I has screw threads engaging those in an opening 62 of a conductorbracket or block 63 within and suitably insulated from thebox orreceptacle and adapted to have a conductor for the other side of thecircuit as at 64 connected thereto. Rod 6I exteriorly of the box orreceptacle is surrounded by a tube 65 of insulation, equipped with anoperating knob 66 and it is turnable with the rod since the latter hasan enlargement 61 engaging a slot 68 of the knob. The tube 65 on itsexterior is preferably weakened at intervals or provided withindications as at 69 enabling portions of the tube 65 at the inner end,to be removed by cutting or fracture, when necessary, to permit inwardadjustment of the fuse rod 6|. Such tube 65 may be made of -hard orelastic rubber or any equivalent material.

Various changes may be resorted to provided they fall within the spiritand scope of the invention.

I claim as my invention:

1. A fuse structure o1' the class described having a contact, a fusemember in engagement with said contact and adapted to burn at the zoneof engagement upon short circuit, and means whereby the fuse member maybe moved into contact thereafter with the contact, comprising screwthreads on the fuse member, and a conductor on the contact operativelyengaged by the screw threads.

2. A fuse structure of the class described having a contact, a fusemember in engagement with said contact and adapted to burn at the zoneof engagement upon shortcircult, means wherebythe fuse member may bemoved into contact thereafter` with the contact, comprising screwthreads on the fuse member, a conductor on the contact operativelyengaged by the screw threads, said contact being of carbon.

3. A fuse structure of the class described having a contact, a fusemember in engagement with said contact and adapted to burn at the zoneoi' engagement upon short circuit, means whereby said engagement of thefuse member and contact may be reestablished thereafter, said contactbeing of quicksilver.

4. A fuse structure of the class described having a contact, a fusemember in engagement with said contact and adapted to burn at the zoneof engagement upon short circuit, means whereby said engagement of thefuse member and contact may be reestablished thereafter, a body mountingthe contact member and fuse member, the latter extending exteriorly ofthe body, and a collapsible insulating member on the fuse memberexteriorly of the body.

5. A fuse structure of the class described having a contact, a fusemember in engagement with said contact and adapted to burn at the zoneof engagement upon short circuit, means whereby said engagement of thefuse member and contact may be reestablished thereafter, a receptaclemounting the contact member and fuse member, insulating means about thescrew member exteriorly of the receptacle, said insulating means havingindications thereon to facilitate fracture to enable adjustment of thefuse member.

6. A fuse structure of the class described having a body, conductormeans extending laterally therefrom for attachment in an electriccircuit, a separated nut and contact in the body in circuit with theconductor means, a fuse 'member screw threaded in said nut andengageable with said contact, said fuse member beingdisposed at an angleto said conductor members.

'7. A fuse structure of the class described having a body, conductormeans extending laterally therefrom for attachment in an electriccircuit, a separated nut and contact in the body in circuit with theconductor means, a fuse member screw threaded in said nut and engageablewith said contact, said fuse member being disposed at an angle to saidconductor members, and extending exteriorly of the body, and collapsibleinsulation about the fuse member exteriorly of the body.

8. A fuse structure of the class vdescribed having a body, a welltherein containing quicksilver, a conductor bar in said body, a contactin said well exposed to the quicksilver, a fuse rod screw threaded tosaid conductor member and engageable at its inner end with saidquicksilver, said body and conductor member having a psage therethroughenabling supply of quicksilver to said well, and a closure for saidpassage.

JOSEPH T. VATAVA.

